The present invention relates to a digital image printing process, particularly useful for printing autostereoscopic images, especially intended to be viewed through a lenticular network.
An image intended to be viewed through a lenticular network is formed from several images that have been cut into strips. FIG. 1 shows the steps of a conventional printing process. As shown in FIG. 1, a starting image is cut into strips 5a-5d of the same width; strips of the same order from each starting image are then arranged contiguously. The image is thus formed of interleaved images 3. A lenticular network is then arranged in front of the image so that all the strips of the images of the same order correspond with the same lens. According to the angle of observation of the image, the observer sees one or the other of the interleaved images. The interleaved images must then be perfectly separated one from each other, i.e., the separation between the different strips must be as sharp as possible so that the observer only sees one image at a time and this must be perfectly clear.
When digital images are printed halftone, a reproduction technique called dithering is sometimes used. This technique simulates the halftones of a black and white image or a color image. Halftones are simulated, either by alternating, according to a selected percentage, the black dots and the white dots for a monochrome print, or by creating a texture that mixes the basic colors, pixel by pixel, according to a set percentage. When interleaved images are to be reproduced and a dithering technique is used, this technique is applied directly to the image that is to be printed, that is to the image constituted by the interleaved images. No allowance is made for the different interleaved images, and the colors are simulated for the whole image 9 formed by the interleaved images. When such an image 9 is printed and viewed through a lenticular network, as the different interleaved images have not been separated precisely, the observer will see different images successively that are not perfectly sharp, and especially see transitions between the images that are blurred in particular because of the dithering algorithm used. Such a process does not allow much flexibility either in the number of images that can be interleaved, or in the number of lines that can be allocated to each of the images.
An object of the present invention is to provide for a halftone printing process for an image comprising several interleaved images that avoids the problems of the prior art.
The invention relates to a halftone type printing process for a digital image I intended to be viewed through a lenticular network comprising a plurality of lenses. The image I comprises a number j of pixel lines and is constituted by a number n of interleaved images. One interleaved strip of each of the n images is in correspondence with one lens. The process comprises the steps of:
a) sampling n images to obtain n digital images comprising a total of j pixel lines;
b) applying a dithering algorithm to each of the n digital images obtained in the preceding step a;
c) cutting each dithered image into a number q of strips comprising an identical number of lines for each dithered image, with the cutting being such that the sum of the pixel line strips of the n images intended to correspond with the same lens equals j/q;
d) constructing the image I by interleaving the strips of n dithered images in order; and
e) printing image I.
The present invention further relates to a halftone type printing process for a digital image I intended to be viewed through a lenticular network comprising a number p of lenses arranged parallel in a first direction, and a number q of lenses arranged parallel in a second direction, with the image I comprising a number j of pixel lines in a first direction and a number k of pixel lines in a second direction and including a matrix of images a*b comprising n images to be interleaved, one strip in a first interleaving direction of each of the a images and/or one strip in a second interleaving direction of each of the b images corresponding with a lens, the process comprises the steps of: sampling n images to obtain b groups of a digital images, with each group comprising in total j pixel lines in the first direction, and/or a groups of b digital images, with each group comprising in total k pixel lines in the second direction; applying a dithering algorithm to each of the n digital images obtained in the sampling step; cutting each of the n dithered images into a number p of strips in the first direction comprising an identical number of lines in the first direction for each dithered image, with the cutting being such that a sum of the pixel lines of the strips in the first direction of each group of a images intended to correspond with the same lens equals j/p; and/or cutting each of the n dithered images into a number q of strips in the second direction comprising an identical number of lines in the second direction for each dithered image, with the cutting being such that a sum of the pixel lines of the strips in the second direction of each group of b images intended to correspond with the same lens equals k/q. The process further comprises the steps of: constructing the image I by interleaving strips 1 to p of the a dithered images in order in the first direction, and/or strips 1 to q of the b dithered images in the second direction; and printing the image I.